System for damping the reflection wave at the open end of a magnetostrictive sensor system

ABSTRACT

The invention relates to a system for damping the reflection wave at the open end ( 6 ) of a magnetostrictive sensor system, which has at least one magnet device ( 2 ), which can be moved relative to a measuring wire ( 1 ) that can be deflected mechanically and that experiences a deflection under the influence of a current pulse ( 3 ), which deflection can be processed by a signal device ( 5 ), wherein the system has at least one damping part ( 8 ) lying against the measuring wire ( 1 ) at the open end ( 6 ), said damping part having a tubular damping element ( 9 ), which can be clamped to the measuring wire ( 1 ) by means of a sleeve-like enclosure ( 11 ). wherein the sleeve-like enclosure ( 11 ) can be deformed from an expanded initial state, which is intended for attaching the sleeve-Lice enclosure to the damping element ( 9 ), to a constricted functional state that exerts a clamping force on the damping element ( 9 ), wherein the method is characterized in that the sleeve-like enclosure ( 11 ) is constricted to all increasing extent from the end ( 19 ) of the sleeve-like enclosure adjacent to the signal device ( 5 ) to the other end ( 19′ ) so that the tube-like damping element ( 9 ) is likewise pressed into a conical contour, and at least the conical contour of the sleeve-like enclosure ( 11 ) is continuous and without interruption.

The invention relates to a system for damping the reflection wave at the open end of a magnetostrictive sensor system, which has at least one magnet device, which can be moved relative to a measuring wire that can be deflected mechanically and that experiences, subject to the influence of a current pulse, a deflection, which can be processed by a signal device, wherein the system has at least one damping part, which rests against the measuring wire at the open end and has a tubular damping element, which can be clamped to the measuring wire by means of a sleeve-like enclosure, wherein the sleeve-like enclosure can be deformed from an expanded initial state, which is provided for attaching a damping element, to a constricted functional state that exerts a clamping force on the damping element.

Magnetostrictive sensor systems are known from the prior art. They are used in a wide range of fields as a displacement measurement system or for determining a position. The core piece of such systems is the measuring wire that is made of a special metal alloy and forms a waveguide. A structure-borne sound wave is generated on this waveguide as a measurement signal. This structure-borne sound wave is induced by the interaction between a permanent magnet, which can be moved along the measuring wire as the position transducer, and a current pulse in the measuring wire. In this way, the structure-borne sound wave is generated as a mechanical pulse, which propagates as the torsional and longitudinal wave beginning at the point of origin at the magnet and going in both directions on the waveguide. The position of the magnet along the measuring section, formed by the measuring wire, can be determined by measuring the runtime of this wave from the point of origin at the magnet up to a signal pickup, which forms a signal converter.

During the measuring process, the wave is reflected at the ends of the waveguide. Since this reflection interferes with the actual measuring process, it has to be damped by a damping system. For this purpose, the prior art provides the open end with a damping part made of a damping material, for example, a soft material, like synthetic rubber, polyurethane, or any other visco-plastic material. The mounting of such materials is relatively complex. In order to rectify this problem, DE 103 48 195 A1 discloses a damping system that conforms to the type described in the introductory part and that has a tubular damping element that is used for the assembly process. This tubular damping element has an expanded initial state, in which it can be easily pushed onto the measuring wire. Then the damping element can be clampingly locked by means of a sleeve-like enclosure in such a way that it exerts a clamping force on the measuring wire and, as a result, is secured on the measuring wire.

While this approach may simplify the assembly and production process, because the tubular damping element and enclosure can be pushed jointly in a loose, non-clamping state, that is, simply and easily, onto the measuring wire, after which the clamping force is applied to the damping part by a shape change of the enclosure, in order to clamp the damping part to the measuring wire, the prior art system cannot achieve an optimal damping effect.

Working on the basis of this prior art, the object of the present invention is to provide a damping system that is distinguished by its improved damping effect while retaining the advantages of the simple and cost-effective production.

The present invention achieves this object with a system having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, an essential feature of the invention resides in the fact that the sleeve-like enclosure is constricted with increasing intensity beginning at the end of the sleeve-like enclosure adjacent to the signal device and going in the direction of the other end, so that the tubular damping element is also pressed into a conical contour, and that at least the conical contour of the sleeve-like enclosure is continuous and without interruption. In contrast, the prior art solution provides that the sleeve-like enclosure is compressed radially at those points that are axially offset from each other, so that individual clamping points are formed, with the penetration depth into the tubular damping element being selected in such a way that it increases from clamping point to clamping point in order to achieve an increasing damping effect in the direction of the free end of the measuring wire. This step by step change in the damping effect is disadvantageous. In particular, it is not possible or hardly possible to reproduce the total damping effect with this configuration. In contrast to the prior art solution, the continuous conical contour of the enclosure leads to a correspondingly conical deformation of the tubular damping element, so that its compression does not increase suddenly, but rather uniformly over its length and, in so doing, provides a continuously increasing degree of damping. Since both the degree of conicity and the length of the sleeve-like enclosure can be chosen, it is possible to achieve an optimal damping in a way that is readily repeatable.

In especially advantageous exemplary embodiments, the conicity of the sleeve-like enclosure is essentially the same. As a result, it is possible to attain a degree of damping that increases in an especially uniform manner.

Preferably, the arrangement is configured in such a way that the tubular damping element extends beyond the two ends of the sleeve-like enclosure and that the measuring wire extends outwardly from the respective end of the tubular damping element especially at both ends of the sleeve-like enclosure. This feature allows an electrical contact to be made with the measuring wire even at the open end.

An enclosure in the form of a metal sleeve can be provided in an especially advantageous way; and this metal sleeve can be constricted by a plastic, mechanical deformation. The sleeve can be pushed together with the tube piece which forms the damping part, loosely over the measuring wire and then deformed in a controlled manner, in order to exert the clamping force on the tube piece. Instead of a deformation of the sleeve by mechanical forces, it is possible to use a sleeve made of a shape memory metal, with the sleeve being expanded in the assembly state and assuming a tight shape by heating.

In the case of a mechanically deformed metal sleeve, the sleeve can have at least one longitudinal bead in the constricted functional state, said longitudinal bead being formed by laying a strip of the sleeve wall alongside itself so that two diametrically opposite longitudinal beads can be formed.

The damping element can be formed by a tube made of a soft material, for example, by a tube made of a silicone rubber.

The invention is explained in detail below in conjunction with an exemplary embodiment shown in the drawings. Referring to the drawings:

FIG. 1 is a representation that is drawn in the manner of a diagram merely to explain the operating mode of a magnetostrictive sensor system;

FIG. 2 is a perspective oblique view of an exemplary embodiment of the inventive damping system that is enlarged by about a factor of 4 over a practical embodiment;

FIGS. 3, 4, and 5 are a top view and a side view and a front view, respectively, of the exemplary embodiment from FIG. 2; and

FIG. 6 is a longitudinal sectional view of the exemplary embodiment that is not drawn to scale and is enlarged even more compared to the embodiment in FIG. 4.

FIG. 1 shows a measuring wire designated as 1 that is used as the waveguide and is made of a ferromagnetic metal alloy. A permanent magnet 2 can be moved, as the position transducer, along the measuring wire 1. Owing to a current pulse 3, generated in the measuring wire 1, the magnet 2 induces a measuring signal in the form of a structure-borne sound wave 4, which issues from the point of origin at the magnet 2 and that propagates in both directions on the measuring wire 1. In order to determine the position of the magnet 2, the travel time of the wave 4 up to a signal pickup is measured, where a signal converter 5 is provided. The signal of the signal converter is evaluated by a signal device that is not illustrated. As indicated in FIG. 1, the signal-giving structure-borne sound wave 4 generates a reflection wave 7. In order to rectify its disturbing influence on the measurement results, the open end 6 of the system has a damping system 8, which is described in detail in conjunction with FIGS. 2 to 6.

FIGS. 2 to 6 show an exemplary embodiment of the damping system 8, in which a longitudinal section of a tube 9 made of silicone rubber is securely clamped on the measuring wire 1. For this purpose, the tube 9 has a metal sleeve 11 in the form of a closed sleeve that is hollow-cylindrical in the initial state. Said hollow cylindrical sleeve extends between its ends 19 and 19′ continuously up to the vicinity of the two ends 13 of the tube 9. FIGS. 2 to 6 show the sleeve 11 in its functional state, in which it is deformed with respect to the initial state. In this deformed functional state, the sleeve 11 is clampingly locked in such a way that each diametrically opposite point has a longitudinal bead 15, which extends continuously over the length of the sleeve. This deformation constricts the sleeve 11 to an extent that a clamping force is exerted on the tube 9, which clamps this tube on the measuring wire 1.

It is clear from FIGS. 4 and 6 that the sleeve 11 is compressed in the functional state in such a way that at one end 19—in the present example, the end 19 that lies the closest to the signal device 5—the sleeve 11 has a larger diameter than at the other end 19′, which is adjacent to the open end 6 of the system. As a result, the internal tube 9 is compressed in such a way that it assumes a slightly conical shape. Since the compression of the tube 9 varies widely over its length, it is possible to achieve a variance in the degree of damping of the damping part 8. Instead of the conical contour of the tube 9 shown in FIG. 4 from left to right in FIG. 4, the conicity could be reversed as a function of the system properties.

As can be seen most clearly in FIG. 6, the metal sleeve 11 is deformed in the illustrated functional state in such a way that it has a conical contour over its entire length. In this case, the conicity is continuous; that is, it is uninterrupted. As a result, the tube 9, forming the damping element, is increasingly compressed beginning at the end adjacent to the signal device 5 and going in the direction of the free end of the measuring wire 1, so that the material of the tube 9 is compressed with continuous increase, so that in turn the degree of damping steadily increases in a continuous manner over the length of the sleeve 11.

In the illustrated exemplary embodiment, the metal sleeve 11 is compressed in such a manner that lateral longitudinal beads 15 are formed. Similarly, the conical constriction could be effected by other measures; or an enclosure made of a shape memory material that assumes a constricted shape on raising the temperature could be provided, as stated above. 

1. A system for damping the reflection wave at the open end (6) of a magnetostrictive sensor system, which has at least one magnet device (2), which can be moved relative to a measuring wire (1) that can be deflected mechanically and that experiences, subject to the influence of a current pulse (3), a deflection, which can be processed by a signal device (5), wherein the system has at least one damping part (8), which rests against the measuring wire (1) at the open end (6) and has a tubular damping element (9), which can be clamped to the measuring wire (1) by means of a sleeve-like enclosure (11), wherein the sleeve-like enclosure (11) can be deformed from an expanded initial state, which is provided for attaching a damping element (9), to a constricted functional state that exerts a clamping force on the damping element (9), characterized in that the sleeve-like enclosure (11) is constricted with increasing intensity beginning at the end (19) of the sleeve-like enclosure adjacent to the signal device (5) and going in the direction of the other end (19′), so that the tubular damping element (9) is also pressed into a conical contour, and that at least the conical contour of the sleeve-like enclosure (11) is continuous and without interruption.
 2. The system according to claim 1, characterized in that the conicity of the sleeve-like enclosure (11) and the damping element (9) is essentially the same.
 3. The system according to claim 1 or 2, characterized in that the tubular damping element (9) extends beyond the two ends (19 and 19′) of the sleeve-like enclosure (11).
 4. The system according to claim 1, characterized in that the measuring wire (1) extends outwardly from the respective end (13) of the tubular damping element (9) at both ends (19 and 19′) of the sleeve-like enclosure (11).
 5. The system according to claim 1, characterized in that the sleeve-like enclosure (11) is provided in the form of a metal sleeve (11), which can be constricted by a plastic, mechanical deformation.
 6. The system according to claim 5, characterized in that the sleeve (11) in the constricted functional state has at least one longitudinal bead (15), which is formed by laying a strip of the sleeve wall alongside itself.
 7. The system according to claim 6, characterized in that two diametrically opposite longitudinal beads (15) are formed.
 8. The system according to claim 7, characterized in that respective longitudinal beads (15) extend over the entire length of the sleeve (11).
 9. The system according to claim 1, characterized in that the damping element is formed by a tube (9) made of a soft material.
 10. The system according to claim 9, characterized in that a tube (9) made of a silicone Tubber is provided. 